--- a/browser/base/content/browser-safebrowsing.js
+++ b/browser/base/content/browser-safebrowsing.js
@@ -1,35 +1,34 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 #ifdef MOZ_SAFE_BROWSING
 var gSafeBrowsing = {
 
   setReportPhishingMenu: function() {
-
     // A phishing page will have a specific about:blocked content documentURI
-    var isPhishingPage = content.document.documentURI.startsWith("about:blocked?e=phishingBlocked");
+    var uri = getBrowser().currentURI;
+    var isPhishingPage = uri && uri.spec.startsWith("about:blocked?e=phishingBlocked");
 
     // Show/hide the appropriate menu item.
     document.getElementById("menu_HelpPopup_reportPhishingtoolmenu")
             .hidden = isPhishingPage;
     document.getElementById("menu_HelpPopup_reportPhishingErrortoolmenu")
             .hidden = !isPhishingPage;
 
     var broadcasterId = isPhishingPage
                         ? "reportPhishingErrorBroadcaster"
                         : "reportPhishingBroadcaster";
 
     var broadcaster = document.getElementById(broadcasterId);
     if (!broadcaster)
       return;
 
-    var uri = getBrowser().currentURI;
     if (uri && (uri.schemeIs("http") || uri.schemeIs("https")))
       broadcaster.removeAttribute("disabled");
     else
       broadcaster.setAttribute("disabled", true);
   },
 
   /**
    * Used to report a phishing page or a false positive